How did Justice Antonin Scalia interpret the Second Amendment’s phrase about a well-regulated militia in District of Columbia v. Heller?

In District of Columbia v. Heller (2008), Justice Antonin Scalia interpreted the Second Amendment by distinguishing between its prefatory and operative clauses. He argued that the preamble—“A well regulated Militia, being necessary to the security of a free State”—does not limit the amendment to militia service.1

Instead, Scalia maintained that the preamble is consistent with an individual-right interpretation when viewed through the lens of the framers' historical context. He reasoned that the founders believed the most effective way to destroy a citizens' militia was to disarm the citizenry; therefore, protecting the individual right to keep and bear arms was seen as essential to maintaining a ready militia.1

By focusing on the operative clause—“the right of the people to keep and bear Arms, shall not be infringed”—the majority concluded that the amendment codifies a pre-existing individual right derived from common law, with self-defense in the home serving as its central component. This interpretation explicitly rejected the "collective-right" theory, which would have restricted firearm possession to those serving in a militia.1